Method and apparatus for papermachine felt cleaning

ABSTRACT

Papermachine felts are cleaned of accumulated debris by impacting same with a high energy, low volume water jet which reciprocates across the felt width continuously at a very low frequency rate coordinated with the felt speed whereby the jet is advanced across the felt between successive felt revolutions by a distance approximately equal to the jet stream width on the felt.

United States Patent [191 Shelor 1 Oct. 7, 1975 METHOD AND APPARATUS FOR PAPERMACHINE FELT CLEANING [75] Inventor: Clifford D. Shelor, Tyrone, Pa.

[73] Assignee: Westvaco Corporation, New York,

22 Filed: Mar. 26, 1974 211 Appl. No; 454,958

[52] U.S. C1. 162/199; 134/15; 134/122;

162/252; 162/262; 162/277; 239/186 [51] Int. Cl. DZlF l/32; B088 3/02 [58] Field of Search 162/199, 198, 252, 262,

[56] References Cited UNITED STATES PATENTS 1,459,161 6/1923 Roberts 162/277 1,859,508 5/1932 Harris 162/277 2,273,126 2/1942 McGillin 134/57 R 3,135,653 6/1964 Smith 162/277 3,739,605 6/1973 Baker 162/277 X FOREIGN PATENTS OR APPLICATlONS 665,506 6/1963 Canada ,1 162/277 Primary ExaminerS. Leon Bashore Assistant Examiner-Richard V. Fisher Attorney, Agent, or FirmW. Allen Marcontell; Richard L. Schmalz [57] ABSTRACT Papermachine felts are cleaned of accumulated debris by impacting same with a high energy, low volume water jet which reciprocates across the felt width c0ntinuously at a very low frequency rate coordinated with the felt speed whereby the jet is advanced across the felt between successive felt revolutions by a distance approximately equal to the jet stream width on the felt. 1

14 Claims, 6 Drawing Figures U.S. Patent Oct. 7,1975 shw 1 of5 3,910,815

US. Patent 0m. 7,1975 Sheet 2 of5 3,910,815

U.S. Patent 0a. 7,1975 Sheet 3 of5 3,910,815

Ill-l JMS m u Q US. Patent 0a. 7,1975 Sheet 5 of5 3,910,815

LOW FREQUENCY OSCILLATOR FELT REV. N0.

% FILLED METHOD AND APPARATUS FOR PAPERMACHINE FELT CLEANING BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the art of papermaking.

More specifically, the present invention relates to the maintenance of paper web carrying felts in a clean and operatively efficient condition.

2. Description of the Prior Art In the papermaking process, an aqueous slurry of cellulose is laid upon the traveling, table surface of an endless belt of screen material. In transit, from one end of the table surface to the other, a major portion of the water vehicle is drawn through the screen cell spaces to leave a loosely matted web of wet cellulose.

At the dry end of the traveling table, the web mat is transferred to a tightly woven fabric belt characterized as a press felt. One function of the press felt is to provide substrate support for the web as it is threaded through a plurality of roll press nips. Another function of the press felt is as an intimate contact moisture wick to draw additional water from the web.

In the course of continuous operation, the press felt will accumulate minute particles of cellulose fiber to fill, coat or otherwise obstruct the porous quality of the felt. Such coatings and fillings greatly inhibit the wicking function of the felt and streak the web carried thereon.

The conventional technique for cleaning a press felt without removal from service is to intermittently direct a multiplicity of high pressure jet streams of water against the felt surface. Typically, such jet streams are spaced across the felt width on six or twelve inch centers and reciprocated in the cross direction with an approximately twelve inch stroke. US Pat. Nos. 1,381,272 and 3,135,653 provide representative descriptions of suitable equipment.

Theoretically, each jet stream will clean a hand area about the felt circumference. With a narrow, high velocity jet stream this is accomplished by repeatedly tracing diagonal lines of jet stream impact against the felt in both directions across the felt band. Although the felt speed and circumference is of consideration to the jet stream traversal velocity, there is no assurance of total felt surface cleaning aside from mathematical probabilities.

U.S. Pat. Nos. 941,750, l,77l,335 and 1,859,508 represent early efforts at total surface cleaning by enlarging the jet stream impact area. Unfortunately, extremely high energy concentrations are necessary to dislodge the troublesome particles from the felt body. By spreading the jet from a singular orifice as taught by these patents, the limited hydraulic energy available at the orifice is distributed over a larger area to reduce the magnitude of energy applied per unit area of felt. Consequently, cleaning is inadequate.

Although the multiplicity of high energy nozzles reciprocated over a relatively short stroke is moderately successful in cleaning the felt, such equipment must be operated on an intermittent schedule since continuous operation would soon destroy the felt. Start and stop scheduling of cleaner operation adds another among many duty burdens on the machine operator of a type not simply automated.

Moreover, since the objective of the press felt is to remove water from the web, all the water added thereunto by the cleaner must be removed; in addition to the relatively small water quantities removed from the web. Accordingly, such high energy, multiple nozzle felt cleaning equipment heavily burdens cooperative water removal equipment.

SUMMARY OF THE INVENTION An objective of the present invention is to teach a method of cleaning a papermaking felt which assures total coverage of the felt area by hydraulic jets having high energy concentration.

Another objective of the present invention is to teach a method of cleaning papermaking felts which requires very little water input to the felt.

Another objective of the present invention is to disclose a simple and reliable apparatus for traversing the entire width of a papermaking felt with a cleaning shower.

Another objective of the present invention is to disclose a continuously operating high energy felt cleaning shower having a traversal rate strictly coordinated with the felt speed.

These and other objectives of the present invention are accomplished with apparatus comprising one or a small number of closely clustered, high energy jet nozzles which are caused to traverse the felt width at an extremely low velocity relative to the felt speed and in strict coordination therewith.

The traversal rate of the cleaning nozzles is either electrically or mechanically paced to advance the noz' zles across the felt by a distance approximately equal to the impact area width of a high energy jet for each revolution of the felt. Accordingly, the entire felt area is systematically cleaned in a single traverse.

BRIEF DESCRIPTION OF THE DRAWINGS Relative to the drawings wherein like reference characters relate to like elements throughout the several figures:

FIG. 1 is a web and felt threading schematic of a papermachine wet-press section.

FIG. 2 is an elevational view of the invention as seen from FIG, I cut lines Il-Il.

FIG. 3 is an end view of the traversing mechanism for the present invention as seen from FIG. 2 cut lines III- III.

FIG. 4 is a plan view of the traversing mechanism for the present invention as seen from FIG. 2 cut lines IVIV.

FIG. 5 shows the trace pattern of a single cleaning jet pursuant to the present invention as it traverses the width of a felt moving thereunder.

FIG. 6 is a graphic display of the operative efficiency of a press felt maintained pursuant to the present invention as compared to the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENT To focus the purpose and use environment of the present invention, reference is first made to the schematic of FIG. I wherein the web press section 20 of E papermachine is shown as located between the fourdrinier l0 and dryer section 30. A loosely consolidatec web W of cellulose fiber is formed on the fourdriniei table 11 from an aqueous slurry of such fiber. From the fourdrinier couch roll 12, the web W is transferred to the first press section 21 and supported on a closed loop fabric belt F, characterized as a felt. Felt F, carries the web W through the nip of a first pair of press rolls 24 where a portion of the water remaining in the web is expressed therefrom by nip pressure and absorbed by the felt.

Depending upon particular machine design, the web W may be passed through one or more additional pressing units such as 22 and 23 wherein the previous steps are repeated through press rolls 25 and 26.

Normally, each press roll unit of the press section 20 is provided with respective felts. Each felt is provided with a cleaning shower C to dislodge accumulated fiber from the felt and suction box S to draw out absorbed water.

The present invention is directed to the felt cleaning shower C which is located ahead (relative to the direction of felt travel) of the suction box S. Further description will be directed to shower C,-, but is typical for showers C and C also.

Relative to FIG. 2 which represents a partially sectioned elevation of shower C there is shown an l-beam support member 27 which exceeds the width of felt F Preferably, the entire length of shower C is protected by a shroud 28.

Referring to FIGS. 2, 3 and 4, a rail assembly 29 is longitudinally secured to the I-beam web for support of a traversing vehicle 40. The traversing vehicle includes frame plates 41 having trolley wheels 42 secured thereto. Depending from the frame plates 41 are a pair of hanger straps 43 supporting a nozzle block 44. One or more exchangeable nozzles are screwed into the block 44 to communicate with internal fluid conduits drilled therein. Also secured to the block 44 for communication with said internal block conduits are piping conduits 46 and 47. Flexible pipes 48 and 49 supply cleaning fluid to the vehicle carried conduits and nozzles from a high pressure (500 psi or greater) stationary source not shown.

The provision of two supply conduits 48 and 49 is a matter of operational flexibility. By supplying only one nozzle 45a from an isolated conduit 46 and supplying the remaining nozzles independently, allows the machine operator to wash with only one nozzle when necessary and to make the change without operational interruption.

Additionally, flexible pipes 48 and 49 may be protected from entanglement and injury by routing them through a line of articulated armor rings 50.

The discharge jet characteristics should be such as to provide the smallest possible area of impact against the felt F so as to concentrate the hydraulic energy available therefrom.

The drive mechanism for the traversing vehicle 40 comprises a flexible belt 60 secured at opposite ends by clasps 61 to a frame plate 41. The belt periphery is threaded over a plurality of sheaves 62, sheave 63 being a drive sheave. The drive sheave 63 is driven by a suitable chain or belt drive mechanism 64 from a stepping motor 65.

The nature of stepping motor 65 is to rotate a power output spindle for a specified number of degrees in response to a power pulse. Cooperative with stepping motor 65 is pulse generator 66 coupled, either mechanically or electrically, to one of the press rolls 26. The nature of pulse generator 66 is to emit a specified number of electrical pulses for each revolution of the coupled press roll 26. Accordingly, the absolute time interim between generator pulses is directly related to the speed of felt F Cooperatively then, the speed of stepping motor 65 is also directly related to the speed of felt F;,.

For additional operational flexibility, a pulsing relay may be provided between generator 66 and motor 65 to proportionalize the number of motor 65 pulses to the number of operating nozzles. In other words, if it is desired to operate only one of four noules on block 44, motor 65 would respond to only one-quarter of the total number of pulses emitted by generator 66.

Also coupled to the traversing vehicle drive belt 60, by tension sheave 67, is a timing switch 68. The collective nature of sheave 67 and switch 68 is to allow fluid flow into supply pipes 48 and 49 so long as the movement of belt rotatively drives sheave 67. Rotation of sheave 67 repeatedly starts timer 68. Should the belt stop, however, the timer 68 will receive no restart signal from sheave 67 and after a predetermined period of time, 9 seconds for example, will interrupt fluid flow to the supply piping 48 and 49. objectively, the felt is protected from jet damage in the event of some system failure.

Direction reversal of the vehicle 40 at the end of a traverse is accomplished by means of proximity switch pairs 51 and 52. When switch element 51a approaches close proximity with cooperative element 51b, polarity of the power circuit to stepping motor is reversed to drive the vehicle 40 in the opposite direction. The opposite result is accomplished by proximity of switch element 52a with cooperative element 52b.

As previously described, stepping motor 65 drives the traversing vehicle 40 at some predetermined speed that is directly related to the felt speed. Relative to FIG. 5, reference is made to the slightly overlapping circles 70,, 70 and 70 which represent the impact area of a fluid jet from nozzle 45a for successive revolutions of the felt F Each impact area 70 70 and 70 has an effective cleaning width w. Accordingly, if only nozzle 45a is operative, the vehicle 40 is translated a distance w for each passage of a felt length L. Felt length L is equivalent to the peripheral distance around the closed loop of felt F FIG. 5 is a graphic trace of this compound movement as seen by cutting the felt for layout in a single plane.

If all nozzles 45 are operative, the translational speed of vehicle 40 would be four times greater for each passage of felt length L.

One operational advantage of the present invention over the prior art is comparatively illustrated by FIG. 6 wherein the percentage of felt interstice fill within a one foot wide band around the felt by fiber and other contaminants is plotted along the ordinate. Continuous operational hours are plotted along the abscissa. The dash line curve represents the prior art technique of allowing the felt to fill over a 7 hour period before cleaning. The present invention is represented by the continuous saw-tooth line wherein the same felt and band width is cleaned by a single nozzle shower operated continuously at a full felt width traversal period of one hour. It should be noted from FIG. 5 that the present invention need not be driven with a reciprocating cycle. The speed range and drive direction flexibility of the stepping motor 65 permits a slow advance of the vehicle 40 across the web in one direction and a rapid return travel. By slowly traversing the felt in only one direction, it is assured that each increment of the belt is regularly cleaned at the optimum period.

Note also from FIG. 5 that the present invention sustains a uniformly high absorption capacity of the felt as compared to the practice heretofore of letting the fabric saturate before cleaning.

Coordinate with FIG. 5 is the fact that approximately only 20 percent of the prior art water flow is required by the present invention per cleaning cycle. For example, prior art cleaning of a 180 inch wide felt would re quire 20 to 30 gallons of water per minute discharged from 15 to 25 nozzles for a 15 minute cleaning interim. The present invention provides more reliably uniform coverage of the felt with only one nozzle discharging l to 1% gallons of water per minute over a 60 cleaning interim.

Over a 24 hour operating interim a typical prior art felt cleaning schedule would include 3, 30 minute shower operating periods staged at 8 hour intervals for a total of 90 shower minutes per 24 hour day. If each of 25 prior art shower nozzles discharged l 9% gallons of water per minute, the total 24 hour water usage would be 3,375 gallons.

min

gal

. X 60 nozzlemin l nozzle X L50 X 24 I day Use of the present invention in lieu of the prior art, therefore, would permit a 36 percent savings in water consumption.

Having disclosed the essence and preferred embodiments of my invention, obvious modifications thereof will occur to those of ordinary skill in the art without departing from the spirit of my invention embodied in the following claims.

I claim:

I. A method of cleaning endless papermaking felts having planar width and closed loop length while moving longitudinally about the periphery of a closed course with a high energy hydraulic jet nozzle secured to a felt traversing vehicle disposed for reciprocatory movement substantially parallel to the plane of an adjacent portion of said felt in directions substantially parallel with the width thereof, said method comprising the steps of:

A. Providing said nozzle with a supply of high energy hydraulic fluid;

B. Directing a jet of said fluid from said nozzle against the surface of said felt, said jet forming an impact area with said felt surface, said impact area having a width dimension measured substantially parallel with said felt width; and,

C. Driving said traversing vehicle along one of said reciprocatory movement directions at a rate approximately equal to said impact area width dimension for each peripheral revolution of said felt about said closed course.

2. A method as described by claim 1 wherein said traversing vehicle includes a plurality of high energy jet nozzles, each nozzle spaced transversely across said felt 2 l 60 gal/day relative to an adjacent nozzle by a distance approximately equal to the width of an impact area of a jet from said nozzles against said felt, said traversing vehicle being advanced across said felt by a distance approximately equal to a summation of the plurality of said impact area widths for each peripheral revolution of said felt.

3. A method as described by claim 1 wherein the entire width of said felt is traversed by said vehicle.

4. A method as described by claim 2 wherein the entire width of said felt is traversed by said vehicle.

5. An apparatus for cleaning papennaking felts having planar width and closed loop length disposed for longitudinal movement about the periphery of a closed course over at least one felt carrying roll, the width of said felt disposed in a linear plane along a portion of said course, said apparatus comprising:

A. A support member disposed transversely across said closed course, parallel with said linear plane and spaced laterally therefrom;

B. A traversing vehicle secured to said support member for longitudinal movement therealong;

C. High energy hydraulic nozzle means secured to said traversing vehicle and directed against the surface of said felt;

D. Means supplying high energy hydraulic fluid connected to said nozzle means for issuing a jet of said fluid therefrom against the surface of said felt to form an impact area therewith, said impact area having a width dimension measured substantially parallel with said felt width;

E. Drive means for moving said felt longitudinally about said closed course;

F. Felt speed sensing means; and

G. Traverse drive means responsive to said felt speed sensing means for driving said traversing vehicle along said support member at a rate approximately equal to said impact area width dimension for each peripherial revolution of said felt about said closed course.

6. Apparatus as described by claim 5 wherein said felt speed sensing means comprises electrical pulse emitting means, the emission of electrical pulses from said emitting means being proportional to the rotational velocity of said felt carrying roll.

7. Apparatus as described by claim 6 wherein said traverse drive means displaces said traversing vehicle by a distance proportional to a discrete number of said pulses.

8. Apparatus as described by claim 5 wherein said traverse drive means comprises operational monitoring means, said monitoring means causing a discontinuance of hydraulic fluid flow to said nozzle means if said traversing vehicle remains unmoved for a predetermined period of time.

9. An apparatus for cleaning papemiaking felts having planar width and closed loop length disposed for longitudinal movement about the periphery of a closed course over at least one felt carrying roll, the width of said felt disposed in a linear plane along a portion of said course said apparatus comprising:

A. A support member disposed transversely across said closed course. parallel with said linear plane and spaced laterally therefrom;

B. A traversing vehicle secured to said support memher for longitudinal movement therealong;

C. High energy hydraulic fluid supply means;

D. A plurality of high energy hydraulic nozzle means secured to said traversing vehicle, in fluid connection with said fluid supply means and directed to issue a high energy jet of said fluid against the surface of said felt, the positionment of said plurality of nozzles being such that the impact areas of said jets against said felt collectively wash a continuous swath of said felt when said felt is moving thereby, said swath having a width dimension measured substantially parallel with said felt width;

E. Drive means for moving said felt longitudinally about said closed course;

F. Felt speed sensing means; and

G. Traverse drive means responsive to said felt speed sensing means for driving said traversing vehicle along said support member at a rate approximately equal to said swath width dimension for each peripheral revolution of said felt about said closed course.

10. Apparatus as described by claim 9 wherein said plurality of nozzles are spaced on said traversing vehicle, each relative to the other, substantially parallel with the width dimension of said felt.

I 1. Apparatus as described by claim 9 wherein said traverse drive means comprises operational monitoring means, said monitoring means causing a discontinuance of fluid flow to said nozzle means if said traversing vehicle remains unmoved for a predetermined period of time.

12. Apparatus as described by claim 9 comprising first fluid connection means between said fluid supply means and one of said plurality of nozzle means and second fluid connection means between said fluid supply means and the remainder of said plurality of nozzle means.

13. Apparatus as described by claim 9 wherein said felt speed sensing means comprises electrical pulse emitting means, the emission of electrical pulses from said emitting means being proportional to the rotational velocity of said felt carrying roll.

14. Apparatus as described by claim 13 wherein said traverse drive means displaces said traversing mechanism by a distance proportional to a discrete number of said pulses. 

1. A METHOD OF CLEANING ENDLESS PAPERMAKING FELTS HAVING PLANAR WIDTH AND CLOSED LOOP LENGTH WHILE MOVING LONGITUDINALLY ABOUT THE PERIPHERY OF A CLOSED COURSE WITH A HIGH ENERGY HYDRAULIC JET NOZZLE SECURED TO A FELT TRAVERSING VEHICLE DISPOSED FOR RECIPROCATORY MOVEMENT SUBSTANTIALLY PARALLEL TO THE PLANE OF AN ADJACENT PORTION OF SAID FELT IN DIRECTIONS SUBSTANTIALLY PARALLEL WITH THE WIDTH THEREOF, SAID METHOD COMPRISING SION MEASURED SUBSTANTIALLY PARALLEL WITH SAID FELT WIDTH, A. PROVIDING SAID NOZZLE WITH A SUPPLY OF HIGH ENERGY HYDRAULIC FLUID, B. DIRECTING A JET OF SAID FLUID FROM SAID NOZZLE AGAINST THE SURFACE OF SAID FELT, SAID JET FORMING AN IMPACT AREA WITH SAID FELT SURFACE, SAID IMPACT AREA HAVING A WIDTH DIMENSION MEASURED SUBSTANTIALLY PARALLEL WITH SAID FELT WIDTH, AND, C. DRIVING SAID TRAVERSING VEHICLE ALONG ONE OF SAID RECIPROCATORY MOVEMENT DIRECTIONS AT A RATE APPROXIMATELY EQUAL TO SAID IMPACT AREA WIDTH DIMENSION FOR EACH PERIPHERAL
 2. A method as described by claim 1 wherein said traversing vehicle includes a plurality of high energy jet nozzles, each nozzle spaced transversely across said felt relative to an adjacent nozzle by a distance approximately equal to the width of an impact area of a jet from said nozzles against said felt, said traversing vehicle being advanced across said felt by a distance approximately equal to a summation of the plurality of said impact area widths for each peripheral revolution of said felt.
 3. A method as described by claim 1 wherein the entire width of said felt is traversed by said vehicle.
 4. A method as described by claim 2 wherein the entire width of said felt is traversed by said vehicle.
 5. An apparatus for cleaning papermaking felts having planar width and closed loop length disposed for longitudinal movement about the periphery of a closed course over at least one felt carrying roll, the width of said felt disposed in a linear plane along a portion of said course, said apparatus comprising: A. A support member disposed transversely across said closed course, parallel with said linear plane and spaced laterally therefrom; B. A traversing vehicle secured to said support member for longitudinal movement therealong; C. High energy hydraulic nozzle means secured to said traversing vehicle and directed against the surface of said felt; D. Means supplying high energy hydraulic fluid connected to said nozzle means for issuing a jet of said fluid therefrom against the surface of said felt to form an impact area therewith, said impact area having a width dimension measured substantially parallel with said felt width; E. Drive means for moving said felt longitudinally about said closed course; F. Felt speed sensing means; and G. Traverse drive means responsive to said felt speed sensing means for driving said traversing vehicle along said support member at a rate approximately equal to said impact area width dimension for each peripherial revolution of said felt about said closed course.
 6. Apparatus as described by claim 5 wherein said felt speed sensing means comprises electrical pulse emitting means, the emission of electrical pulses from said emitting means being proportional to the rotational velocity of said felt carrying roll.
 7. Apparatus as described by claim 6 whereiN said traverse drive means displaces said traversing vehicle by a distance proportional to a discrete number of said pulses.
 8. Apparatus as described by claim 5 wherein said traverse drive means comprises operational monitoring means, said monitoring means causing a discontinuance of hydraulic fluid flow to said nozzle means if said traversing vehicle remains unmoved for a predetermined period of time.
 9. An apparatus for cleaning papermaking felts having planar width and closed loop length disposed for longitudinal movement about the periphery of a closed course over at least one felt carrying roll, the width of said felt disposed in a linear plane along a portion of said course said apparatus comprising: A. A support member disposed transversely across said closed course, parallel with said linear plane and spaced laterally therefrom; B. A traversing vehicle secured to said support member for longitudinal movement therealong; C. High energy hydraulic fluid supply means; D. A plurality of high energy hydraulic nozzle means secured to said traversing vehicle, in fluid connection with said fluid supply means and directed to issue a high energy jet of said fluid against the surface of said felt, the positionment of said plurality of nozzles being such that the impact areas of said jets against said felt collectively wash a continuous swath of said felt when said felt is moving thereby, said swath having a width dimension measured substantially parallel with said felt width; E. Drive means for moving said felt longitudinally about said closed course; F. Felt speed sensing means; and G. Traverse drive means responsive to said felt speed sensing means for driving said traversing vehicle along said support member at a rate approximately equal to said swath width dimension for each peripheral revolution of said felt about said closed course.
 10. Apparatus as described by claim 9 wherein said plurality of nozzles are spaced on said traversing vehicle, each relative to the other, substantially parallel with the width dimension of said felt.
 11. Apparatus as described by claim 9 wherein said traverse drive means comprises operational monitoring means, said monitoring means causing a discontinuance of fluid flow to said nozzle means if said traversing vehicle remains unmoved for a predetermined period of time.
 12. Apparatus as described by claim 9 comprising first fluid connection means between said fluid supply means and one of said plurality of nozzle means and second fluid connection means between said fluid supply means and the remainder of said plurality of nozzle means.
 13. Apparatus as described by claim 9 wherein said felt speed sensing means comprises electrical pulse emitting means, the emission of electrical pulses from said emitting means being proportional to the rotational velocity of said felt carrying roll.
 14. Apparatus as described by claim 13 wherein said traverse drive means displaces said traversing mechanism by a distance proportional to a discrete number of said pulses. 